Question: A controversial 1992 Danish study9 reported that men's average sperm count has decreased from 113 million per milliliter in 1940 to 66 million per milliliter in 1990.
(a) Express the average sperm count, S, as a linear function of the number of years, t, since 1940.
(b) A man's fertility is affected if his sperm count drops below about 20 million per milliliter. If the linear model found in part (a) is accurate, in what year will the average male sperm count fall below this level?